The similar LOTR deluxe was only issued in a slipcase up to 1974. As Deagol says on his website (for LOTR) "in 1974 the slipcase was replaced by a box with a printed label on the lid. Presumably the decision had been made to replace the slipcase with a box, but existing stocks of slipcases were used up before the change was made."

It would seeem odd therefore for a 1980 Poems and Stories to be in a slipcase though the seller makes a clear statement that the book "was provided by the company without the label usually attached to the front of the sleeve."